silent failure(s) for extension not loading

A partner created an extension in the web app (using github) using micro:bit editor before we updated. After the update, this extension doesn't load (silently fails) and the console has a very uninformative message (see below). The failure is due to the fact that the extension is being loaded in the new editor but asking for files from the old editor (according to @abchatra).

Unhandled rejection TypeError: Cannot read property 'dependencies' of null at https://pxt.azureedge.net/blob/cd6f2fb5d3ebbad2eed435b28e41ba09de50c475/pxtapp.js:1:230686From previous event: at S.L [as _captureStackTrace] (https://pxt.azureedge.net/blob/5d9eb71a9f5a03538833b2d07eb04b0f0d869753/main.js:1:982260) at S._then (https://pxt.azureedge.net/blob/5d9eb71a9f5a03538833b2d07eb04b0f0d869753/main.js:1:1007761) at S.then (https://pxt.azureedge.net/blob/5d9eb71a9f5a03538833b2d07eb04b0f0d869753/main.js:1:1006124) at e.installGh (https://pxt.azureedge.net/blob/5d9eb71a9f5a03538833b2d07eb04b0f0d869753/main.js:1:741343) at e.handleClick (https://pxt.azureedge.net/blob/5d9eb71a9f5a03538833b2d07eb04b0f0d869753/main.js:1:748571) at c (https://pxt.azureedge.net/blob/5d9eb71a9f5a03538833b2d07eb04b0f0d869753/main.js:1:209122) at Object. (https://pxt.azureedge.net/blob/5d9eb71a9f5a03538833b2d07eb04b0f0d869753/main.js:1:1385228) at _ (https://pxt.azureedge.net/blob/5d9eb71a9f5a03538833b2d07eb04b0f0d869753/main.js:1:1385266) at https://pxt.azureedge.net/blob/5d9eb71a9f5a03538833b2d07eb04b0f0d869753/main.js:1:1385412 at x (https://pxt.azureedge.net/blob/5d9eb71a9f5a03538833b2d07eb04b0f0d869753/main.js:1:1385498) at T (https://pxt.azureedge.net/blob/5d9eb71a9f5a03538833b2d07eb04b0f0d869753/main.js:1:1385920) at C (https://pxt.azureedge.net/blob/5d9eb71a9f5a03538833b2d07eb04b0f0d869753/main.js:1:1385755) at A (https://pxt.azureedge.net/blob/5d9eb71a9f5a03538833b2d07eb04b0f0d869753/main.js:1:1386103) at xn (https://pxt.azureedge.net/blob/5d9eb71a9f5a03538833b2d07eb04b0f0d869753/main.js:1:1413049) at le (https://pxt.azureedge.net/blob/5d9eb71a9f5a03538833b2d07eb04b0f0d869753/main.js:1:1499740) at Tn (https://pxt.azureedge.net/blob/5d9eb71a9f5a03538833b2d07eb04b0f0d869753/main.js:1:1413654) at On (https://pxt.azureedge.net/blob/5d9eb71a9f5a03538833b2d07eb04b0f0d869753/main.js:1:1414611) at An (https://pxt.azureedge.net/blob/5d9eb71a9f5a03538833b2d07eb04b0f0d869753/main.js:1:1413899) at s.unstable_runWithPriority (https://pxt.azureedge.net/blob/5d9eb71a9f5a03538833b2d07eb04b0f0d869753/main.js:1:1504531) at Wi (https://pxt.azureedge.net/blob/5d9eb71a9f5a03538833b2d07eb04b0f0d869753/main.js:1:1429490) at ae (https://pxt.azureedge.net/blob/5d9eb71a9f5a03538833b2d07eb04b0f0d869753/main.js:1:1498353) at https://pxt.azureedge.net/blob/5d9eb71a9f5a03538833b2d07eb04b0f0d869753/main.js:1:1413188

Reproduce the partner extension installation in the updated web editor, then trace the installGh and handleClick entry points shown in the console stack. The fix is complete when extensions created before the editor update load successfully or present an informative failure instead of silently rejecting.